As it is known, in rotary stamping machines two cylinders work, between which the piece to be stamped is placed, while one of the cylinders includes the blades of the die itself, while the other functions as the stamping base.
This cylinder that works as the base for stamping is made of steel, and to ensure that the blades of the die are not damaged during stamping, it is equipped with a dolly made of a relatively soft material, usually polyurethane.
More specifically, the said dolly takes the form of a thick band that surrounds the cylinder, I.e., it forms a type of casing that is also cylindrical, with the particularity that it has two metal shapes in the area of its opening, which together form a key that fits into a groove or keyway, where in some cases the said key is affixed by bolts and in others by different means.
The problem with dollies or counter-dies of this type is that they do not have good dimensional stability that would make it possible to maintain the circumferential diameter throughout the whole lifetime of the device, as its support lacks rigidity, making them liable to suffer dilation due to thermal effects.
Additionally it should be pointed out that devices of this type are difficult to implement, giving rise to high maintenance costs due to the long times machines have to be taken out of service so that they can be replaced.
Apart from the problem described above, it also has to be said that counter-dies do not usually fit the cylinder perfectly, making it possible for them to move in certain ways that are negative for the stamping process.